SOI technology may be used for power integrated circuits, as it provides effective isolation of devices and low leakage currents within devices. SOI technology provides the isolation of the structures from the substrate by the introduction of an insulator layer, typically formed from a buried silicon oxide (BOX). In addition, isolation of the device structures of a device from nearby devices may be provided by deep trench isolation (DTI).
Conventional SOI power devices may suffer from a low breakdown voltage because electrostatic potential distribution cannot be spread into a substrate due to the existence of a buried oxide layer.
To overcome these problems, partial SOI (PSOI) technology may be used. PSOI devices make use of both a BOX layer and depletion of the handle wafer to support the breakdown voltage of the device. PSOI technology typically allows better off-state characteristics than those seen with SOI technology, and may also offer advantages such as higher switching speeds, as the BOX layer may be thinner, lower drain to handle wafer capacitance and aiding dissipation of heat generated in the device.
PSOI devices are typically manufactured to have an aperture in the BOX layer at a drain or anode end of the device. PSOI devices may also comprise oppositely doped semiconductor regions to form a buried diode isolated physically from the device structure.